Hydraulic servo-system



18, J. MERC|ER Re.

HYDRAULI C SERVO-SYSTEM Original Filed June 27. 1961 Unted States PatentO 26,195 HYDRAULIC SERVO-SYSTEM Jean Mercier, 501 Bloomfield? Ave.,Caldwell, NJ. 07006 Original No. 3,152,448, dated Oct. 13, 1964, Ser.No. 120,081, June 27, 1961. Application for reissue Oct. 5, 1966, Ser.No. 589,172

4 Claims. (Cl. 60-54.5)

Matter enclosed in heavy brackets appears in the original patent butforms no part of this reissue snecification: matter printed in italicsindicates the additions made by reissue.

This invention relates to the art of servo-systems, more particularly ofthe hydraulic type.

It is among the objects of the invention to provide a hydraulicservo-system which has but relatively few parts, not likely to becomederanged even with long use, that is relatively simple to construct andincludes a transmitter that may be operated with but a relatively simplemanipulation, to deliver fluid under pressure to a hydraulicallycontrolled unit to effect displacement of such unit by an amountproportional to the displacement of the transmitter and which willautomatically compensate for variations in ambient temperature that maycause thermal expansion or contraction of the hydraulic fluid in thesystem and which also may readily be reset for calibration thereof.

According to the invention, these objects are accomplished by thearrangement and combination of elements hereinafter described and moreparticularly recited in the claims.

This application is a continuation-in-part of copending applicationSerial No. 42,000, filed July 12, 1960, now abandoned.

In the accompanying drawings in which is shown one or more of variouspossible embodiments of the several features of the invention,

FIG. 1 is a diagrammatic view of one embodiment of the system, and

FIG. 2 is a view similar to FIG. 1 of another embodiment.

Referring now to the drawings, the servo-system includes a hydraulicpressure transmitter 10, desirably comprising a substantiallycylindrical casing 11 having end walls 12 and 13 and having a piston 14slidably mounted therein with a piston rod 15 atiixed at one end theretoand having its other end extending through the end wall 13. Suitablecontrol means 16 are provided to move the piston 14 from one end of thecasing 11 to the other.

Each of the end walls 12 and 13 of the casing 11 has a port 17 and 18.The port 17 is connected by line 19 to the port 21 of a selector valve22, said valve having additional ports 23 and 24. In one position of thevalve, the ports 21 and 24 are connected and in another position of thevalve, the ports 23 and 24 are connected.

The port 23 of valve 22 and the port 18 of casing 11 are connectedrespectively by lines 25 and 26 to junction 27 which in turn isconnected by line 28 to the oil port 29 of a pressure vessel 31,illustratively a pressure accumulator of any conventional type.

As illustratively shown, the pressure accumulator comprises a rigidcasing 32 in which a deformable partition 36, preferably a bladder, ispositioned, said bladder being designed to be charged with fluid such asgas under pressure through port 34 and the pressure vessel beingdesigned to be charged with fluid such as oil under pressure, slightlyabove atmospheric, through line 35 which is thereafter closed by a valve36.

The pressure transmitter 10 is designed to control a hydraulic unit 41,which also desirably comprises a substantially cylindrical casing 42having end walls 43 and 44 and having a piston 45 slidably mountedtherein, said piston having a piston rod 46 ailixcd thereto at one endand having its other end extending through the end wall 44, said pistonrod controlling any suitable movable member. The end wall 43 ofhydraulic unit 41 has a port 47 connected by line 48 to port 24 of valve22 and the end wall 44 has a port 49 connected by line 51 to a port 52in end wall 13 of pressure transmitter 10.

In the embodiment shown, the dimensions of the pressure transmitter 10and the hydraulic unit 41 are so selected that when the pistons 14 and45 thereof are in the central position in the associated casings 11 and42, the volume of chamber A1 will be substantially equal to the volumeof chamber B1 and the volume of chamber A2 will be substantially equalto that of chamber B2 and the effective area of each of the surfaces ofpistons 14 and 45 in chambers A, B, is greater than that of the surfacesof said pistons in chambers A2, B2 due to the piston rods in said latterchambers.

In the operation of the unit, assuming that the chambers A1, A2 and B1,B2 are lled with fluid and that the pistons 14 and 45 are in the centralposition shown, with valve Z2 connecting ports 21, 24, if the piston 14is moved to the left, such movement of piston 14, will force uid fromchamber A1 into chamber B1, thereby causing the piston 45 to move to theright a corresponding amount.

If piston 14 is moved to the right from the central position, thepressure in chamber B1 on the left side of piston 45 will fall to zeroand since the chamber B2 is subjected to the pressure in the accumulator31, as well as that from chamber A2, the piston 45 will `move to theleft by an amount related to the movement of piston 14 to the right.

If, `for example, due to leakage past the pistons in the units 10 and41, they should become out of alignment, i.e., when the piston 14 ofpressure transmitter 10 is in its central position the piston 45 ofhydraulic unit 41 should be to the left or right of its central positionthe system may readily be calibrated.

To this end, with the valve 22 in position connecting ports 21 and 24,the piston 14 is moved to the extreme left. Thereupon, the valve 22 isturned to connect ports 23 and 24. At this time, the chamber B1 will beconnected directly to the accumulator and chamber A1 cut ott andalthough the chamber B2 is also connected to the accumulator, due to thegreater active area of the lett side of piston 45 which does not havethe piston rod 46 connected thereto, the piston 45 will be moved by theaccumulator pressure in chamber B1 to its extreme right position.

In the embodiment shown in FIG. 2, which is substantially identical tothat shown in FIG. 1, identical parts have the same reference numeralsprimed.

In the embodiment of FIG. 2, the valve 22' in one position to connectports 21 and 24' ond position to connect ports 21 and 23'.

Thus, in normal operation of the embodiment shown in FIG. 2, when ports21' and 24' of valve 22' are connected, when the piston 14' is moved tothe left, the piston 45 will be moved to the right. If piston 14' ismoved to the right the pressure in chamber B'1 to the left of piston 45will fall to zero and since the chamber B2 is connected to theaccumulator 31' the piston 45' will be moved to the left.

To reset the system shown in FIG. 2, in the event the pistons are out ofalignment, the valve 22' is positioned so that ports 2l' and 23 areconnected. This effectively seals the port 47 of chamber B1 so that noHuid can escape or be discharged therefrom. The piston 14' oftransmitter 10 is then moved by member 16 to `a position on itsindicator 60a corresponding to the position of the piston 45 of unit 41on its indicator 60b. Thereupon,

is designed and in a secfor normal operation of the device, the valve22' so that ports 21' and 24' are connected.

1t is apparent from the foregoing that when the piston 14, 14 ofpressure transmitters 10, 10' is moved either to the left or to theright in normal operation of the unit, the piston 4S, 4S of hydraulicunit 41, 41 will move in the opposite direction an amount directlyproportional to the amount of movement of the piston 14, 14' of pressuretransmitter 10. and the position of the piston 45, 45 and the movablemember controlled thereby will be shown by indicators 60a, 60h, 60a,60'b. Thus, remote control may readily be effected of the movablemember, such as a bulkhead door from, say, the bridge of a ship.

In the event of thermal expansion of the hydraulic uid in the system,the resultant increase of the volume of the fiuid and resultant increasein pressure will cause excess fiuid to flow into the accumulator `31,31' to avoid the possibility of rupture of any portion of the system.

In the event of thermal contraction of the hydraulic fluid in thesystem` the resultant decrease in the volume of the fiuid will causedecrease in pressure so that due to the pressure on the fiuid in theaccumulator 31, 3l', fiuid will flow from the accumulator into chambersA2 and B2; A'2 and B'2 of the system when the valve 22, 22' is in theposition shown and thereupon the system may then be recalibrated in themanner above described to compensate for descrease in the amount oftiuid in chambers A1, B1 and A'1. B'1.

It is of course to be understood that the position of the hydraulic unit41, 41' may readily be transmitted to the location of the transmitter10, 10 by any suitable electrical system.

With the relatively simple system above described, movement of ahydraulically controlled unit by an amount proportional to thedisplacement of the movement of the transmitter may readily beaccomplished and resetting of such units may also be readilyaccomplished, by a simple manipulation.

As many changes could tbe made in the above constructions and manyapparently widely different embodiments of this invention could be madewithout departing from the scope of the claims, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be intrepreted as illustrative and not in a limitingsense.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. A hydraulic servo-system comprising a pressure transmitter comprisinga casing having a piston slidably mounted therein, a hydraulic unitcomprising a casing also having a piston slidably mounted therein, saidpistons defining a chamber on each side thereof in the respectivecasings, means connecting the chambers on the respective sides of saidpistons, the volume of the chambers defined on each side of the pistonof the pressure transmitter when said pistons are in central positionbeing at least equal to the volume of the corresponding chambers definedon each side of the piston of the hydraulic unit, whereby movement ofthepiston of the pressure transmitter will provide a movement of the pistonof the hydraulic unit an amount proportional to such first movement,means providing a source of liuid under pressure greater thanatmospheric, the means connecting the chambers on the respective sidesof the pistons comprising a permanent connection between correspondingchambers ou one side of the pistons of said pressure transmitter andsaid hydraulic unit with said source of fluid under pressure, and valvemeans interposed between said source of fiuid under pressure and thechamers of said transmitter and said hydraulic unit on the other side ofthe pistons thereof, said valve means providing communicationalternately between said last two chambers and between one of said lasttwo chambers and the source of fluid for recharging of said transmitterand said hyis set draulic unit upon reduction in the volume of the fluidtherein.

2. A hydraulic servo-system comprising a pressure transmitter unit and ahydraulic unit, each including a casing having a piston slidably mountedtherein, and defining a chamber on each side thereof, each of saidypistons having a piston rod secured thereto and extending through oneend of the associated unit, `whereby the effective area of the pistonsin the chambers defined on one side thereof will be greater than theeffective arcas of the pistons in the chambers defined on the other sidethereof, the volume of the chambers defined on each side of the pistonof the pressure transmitter when said pistons are in central positionbeing at least equal to the volume of the corresponding chambers definedon each side of the piston of the hydraulic unit, a source of fiutidunder pressure greater than atmospheric, a ttwo position valve having atleast three ports, means connecting the first land second of said portsto the chambers of the tpressure transmitter and the hydraulic units inwhich the larger effective area of the associated piston is exposed,means connecting the third of said ports to said source of uid underpressure and to the -chamber of said pressure transmitter in which thesmaller effective area of the associated piston is exposed, meansconnecting said last named chamber of said pressure transmitter and thecorresponding chamber of said hydraulic unit, and means in one positionof said valve to connect the first and second ports and shut off saidthird port and in a second position to connect said second and thirdports and shut off said first port.

3. A hydraulic servo-system comprising a pressure transmitter unit and ahydraulic unit, each including a casing having a piston slidably mountedtherein, and delining a chamber on each side thereof, each of saidpistons having a piston rod secured thereto and extending through oneend of the associated unit, whereby the effective area ofthe pistons inthe chambers defined on one side thereof will be greater than theeffective area of the pistons in the chambers defined on the other sidethereof, the volume of the chambers defined on each side of the pistonof the pressure transmitter when said pistons are in central positionbeing at least equal to the volume of the corresponding chambers definedon each side of the piston of the hydraulic unit, a source of fluidunder pressure greater than atmospheric, a two position valve having atleast three ports, means connecting the first and second of said portsto the chambers of the pressure transmitter and the hydraulic units inwhich the larger effective area of the associated piston is exposed,means connecting the third of said ports to said source of fluid underpressure and to the chamber of said pressure transmitter in which thesmaller effective tarea of the associated piston is exposed, meansconnecting said last named chamber of said tpressure transmitter and thecorresponding chamber of said hydraulic unit, and means in one positionof said valve to connect the first and second ports and shut off saidthird port and in a second position to connect said first and thirdports and shut off said second port.

4. A hydraulic servo-system comprising a pressure transmitter unit and ahydraulic unit, each including a casing having a piston slidably mountedtherein, and defining a chamber on each side thereof, each of saidpistons having a piston rod secured thereto and extending through oneend of the associated unit, whereby the eeclive area 0f the pistons inthe chambers defined on one side thereof will be greater than theeffective areds of the pistons in the chambers defined on the other sidethereof, the volume of the chambers defined on each side of the pistonof the pressure transmitter when said pistons are in central positionbeing at [east equal to the volume of the corresponding chambers definedon each side of the piston of the hydraulic unit, a source of fiuidunder pressure greater than atmospheric, means providing communicationbetween the chambers of the pressure transmitter and the hydraulic unitin which the larger effective area of the associated piston is exposed,means providing communication between the chambers of the pressuretransmitter and the hydraulic unit in which the smaller eective area ofthe associated piston is exposed, and valve means having a resetposition in which communication to one of the chambers of said hydraulicunit is cut O and the remaining chamber of said hydraulic unit and thetwo chambers of said pressure transmitter are connected to said sourceof fluid under pressure and an operating position in which therespective pairs of chambers o] said pressure transmitter and saidhydraulic unit are connected and the source of fluid ander pressure iscut ojj from the chambers of said pressure transmitter in which thelarger eective area of the associated piston is exposed.

References Cited by the Examiner The following references, cited by theExaminer, are of record in the patented le -of this patent or theoriginal patent.

UNITED STATES PATENTS 568,736 10/1896 Brown 6()-54.5 2,315,270 3/1943Palmer {S0-54.5 2,540,879 2/1951 Hebe] et al 60--54.5 2,558,684 6/1951Haase 60-54,5 X 2,669,096 2/1954 MacDuff 60-54.5 3,040,533 6/1962Heinrich 60-54.5

MARTIN P. SCHWADRON, Primary Examiner R. R. BUNEVICH, AssistantExaminer.

